I saw a model specific line drawing that was posted in another thread by YGIDROP of Top Car Detail in Spain.

Curious, I started hunting around the web and found this

Model specific line drawings for a vehicle that they are detailing:

The-Blueprints.com - The largest free blueprint collection on the Internet

On the website, you have to buy them, but you could do a Google Image search for example "2013 C7 Corvette line drawing blueprints" and then print it from there.

Might be another professional element to add to your business.